U.S. patent application number 11/151341 was filed with the patent office on 2006-02-02 for golf ball.
This patent application is currently assigned to SRI Sports Limited. Invention is credited to Seiichiro Endo, Masatoshi Yokota.
Application Number | 20060025238 11/151341 |
Document ID | / |
Family ID | 35733063 |
Filed Date | 2006-02-02 |
United States Patent
Application |
20060025238 |
Kind Code |
A1 |
Endo; Seiichiro ; et
al. |
February 2, 2006 |
Golf ball
Abstract
Golf ball 2 has a spherical core 4, a mid layer 6 covering this
core 4, a reinforcing layer 8 covering this mid layer 6, and a
cover 10 covering this reinforcing layer 8. Base polymer of this
mid layer 6 includes an ionomer resin as a principal component.
Base polymer of this cover 10 includes a thermoplastic polyurethane
elastomer as a principal component. The cover 10 has a thickness Tc
of equal to or less than 0.6 mm. The cover 10 has a hardness Hc as
measured with a Shore D type hardness scale of equal to or less
than 54. The cover 10 has a volume V of equal to or less than 3.0
cm.sup.3. A product obtained by multiplying the thickness Tc, the
hardness Hc and the volume V is equal to or less than 90. The
reinforcing layer 8 includes a thermosetting resin as a base
polymer. The reinforcing layer has a thickness of 3 .mu.m or
greater and 50 .mu.m or less.
Inventors: |
Endo; Seiichiro; (Kobe-shi,
JP) ; Yokota; Masatoshi; (Kobe-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
SRI Sports Limited
|
Family ID: |
35733063 |
Appl. No.: |
11/151341 |
Filed: |
June 14, 2005 |
Current U.S.
Class: |
473/371 |
Current CPC
Class: |
A63B 37/0031 20130101;
A63B 37/0076 20130101; A63B 37/0033 20130101; A63B 37/0003
20130101; A63B 37/12 20130101 |
Class at
Publication: |
473/371 |
International
Class: |
A63B 37/04 20060101
A63B037/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2004 |
JP |
2004-221003 |
Claims
1. A golf ball which comprises a spherical core, a mid layer
positioned outside of the core, and a cover positioned outside of
the mid layer, said cover having a thickness Tc of equal to or less
than 0.6 mm, said cover having a hardness Hc as measured with a
Shore D type hardness scale of equal to or less than 54, said cover
having a volume V of equal to or less than 3.0 cm.sup.3, and
product obtained by multiplying the thickness Tc (mm) the hardness
Hc and the volume V (cm.sup.3) of said cover being equal to or less
than 90.
2. The golf ball according to claim 1 wherein product obtained by
multiplying the hardness (Hc) and the volume V (cm.sup.3) of said
cover is equal to or less than 140.
3. The golf ball according to claim 1 wherein a principal component
of the base polymer of said cover is a thermoplastic polyurethane
elastomer.
4. The golf ball according to claim 3 wherein a principal component
of the base polymer of said mid layer is an ionomer resin.
5. The golf ball according to claim 4 wherein a reinforcing layer
is provided which comprises a thermosetting resin as a base polymer
between said mid layer and said cover, and said reinforcing layer
has a thickness of 3 .mu.m or greater and 50 .mu.m or less.
Description
[0001] This application claims priority on Patent Application No.
2004-221003 filed in JAPAN on Jul. 29, 2004, the entire contents of
which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to golf balls. More
particularly, the present invention relates to multi piece golf
balls having a core, a mid layer and a cover.
[0004] 2. Description of the Related Art
[0005] Top concern to golf players for golf balls is their flight
performances. The golf players particularly place great importance
on flight distance yielded upon shots with a driver. The golf
players also place great importance on flight distance yielded upon
shots with a long iron and a middle iron.
[0006] Golf players also place great importance on spin
performances of the golf balls. Great back spin rate results in
small run. For golf players, golf balls which are liable to be spun
backwards are apt to be rendered to stop at a targeted position.
Great side spin rate results in easily curved trajectory of the
golf ball. For golf players, golf balls which are liable to be spun
sidewise are apt to allow the trajectory to curve intentionally.
Golf balls that are excellent in spin performances are excellent in
control performances. High-level golf players particularly place
great importance on control performances upon shots with a short
iron.
[0007] Feeling experienced upon impact of a golf ball is also
important for high-level golf players. The golf players prefer soft
feel upon impact as well as light feel upon impact. The golf
players also prefer feeling to allow the launch direction to be
readily controlled.
[0008] In light of the flight performances, control performances
and feelings, golf balls having a variety of structures have been
proposed. For example, U.S. Pat. No. 6,106,415 discloses a golf
ball having a core, a mid layer comprising an ionomer resin and a
cover comprising polyurethane.
[0009] Covers having high elasticity are advantageous in terms of
the flight performance. However, the highly elastic covers liable
to deteriorate the control performance and feeling. Soft covers are
advantageous in terms of the control performance. However, the soft
covers are disadvantageous in terms of the flight performance.
Demands from the golf players for golf balls have increasingly
escalated in recent years. Highly balanced flight performances,
control performances and feelings have been desired. An object of
the present invention is to provide golf balls exhibiting excellent
flight performances, control performances and feelings.
SUMMARY OF THE INVENTION
[0010] A golf ball according to the present invention has a
spherical core, a mid layer positioned outside of this core, and a
cover positioned outside of this mid layer. This cover has a
thickness Tc of equal to or less than 0.6 mm. This cover has a
hardness Hc as measured with a Shore D type hardness scale of equal
to or less than 54. This cover has a volume V of equal to or less
than 3.0 cm.sup.3. Product obtained by multiplying the thickness Tc
(mm), the hardness Hc and the volume V (cm.sup.3) of this cover is
equal to or less than 90.
[0011] Preferably, product obtained by multiplying the hardness
(Hc) and the volume V (cm.sup.3) of the cover is equal to or less
than 140.
[0012] Preferably, principal component of the base polymer of the
cover is a thermoplastic polyurethane elastomer. Preferably,
principal component of the base polymer of the mid layer is an
ionomer resin. Preferably, a reinforcing layer is provided, which
comprises a thermosetting resin as a base polymer, between the mid
layer and the cover. This reinforcing layer has a thickness of 3
.mu.m or greater and 50 .mu.m or less.
[0013] A shot with a short iron results in a small amount of
deformation of the golf ball due to low head speed. Upon the shot
with the short iron, spin rate predominantly depends on the
material of the cover surface. Because the golf ball according to
the present invention has a cover having a hardness Hc of equal to
or less than 54, slipping that occurs between the club face and the
golf ball upon impact is suppressed. According to this golf ball, a
great spin rate is achieved upon a shot with a short iron. This
golf ball is excellent in a control performance upon a shot with a
short iron.
[0014] Upon a shot with a driver, the mid layer and the core are
also deformed greatly in addition to the cover. Covers having a low
hardness Hc may be disadvantageous in terms of resilience
performances, however, less adverse effects are exerted on the
resilience performance because this cover is extremely thin. This
golf ball is excellent in a flight performance upon a shot with a
driver.
[0015] Spin rate predominantly depends on deformative behavior of
the cover upon a shot with a long iron and a middle iron. Because
this cover has a small volume V, the amount of deformation is small
irrespective of the hardness Hc being small. Spin rate upon impact
of this golf ball with a long iron or a middle iron is low. Low
spin rate leads to a great flight distance. This golf ball is
excellent in a flight performance upon a shot with a long iron and
a middle iron.
[0016] Because this golf ball has a product obtained by multiplying
the thickness Tc (mm), the hardness Hc and the volume V (cm.sup.3)
of equal to or less than 90, it easily gets on a clubface upon
impact with a driver, and can be favorably delivered from the club.
The getting on the clubface is responsible for stabilization of the
launch direction of the golf ball. Favorable delivery of the ball
results in a light feel at impact. According to this golf ball, an
excellent feeling is experienced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a partially cut off cross-sectional view
illustrating a golf ball according to one embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The present invention is hereinafter described in detail
with appropriate references to the accompanying drawing according
to the preferred embodiments.
[0019] A golf ball 2 depicted in FIG. 1 has a spherical core 4, a
mid layer 6 covering this core 4, a reinforcing layer 8 covering
this mid layer 6, and a cover 10 covering this reinforcing layer 8.
Numerous dimples 12 are formed on the surface of the cover 10. Of
the surface of the cover 10, a part except for the dimples 12 is a
land 14. Although this golf ball 2 has a paint layer and a mark
layer to the external side of the cover 10, these layers are not
shown in the Figure.
[0020] This golf ball 2 has a diameter of from 40 mm to 45 mm. From
the standpoint of conformity to a rule defined by United States
Golf Association (USGA), the diameter is preferably equal to or
greater than 42.67 mm. In light of suppression of the air
resistance, the diameter is preferably equal to or less than 44 mm,
and more preferably equal to or less than 42.80 mm. Weight of this
golf ball 2 is 40 g or greater and 50 g or less. In light of
attainment of great inertia, the weight is preferably equal to or
greater than 44 g, and more preferably equal to or greater than
45.00 g. From the standpoint of conformity to a rule defined by
USGA, the weight is preferably equal to or less than 45.93 g.
[0021] The core 4 is obtained through crosslinking of a rubber
composition. Examples of preferred base rubber include
polybutadienes, polyisoprenes, styrene butadiene copolymers,
ethylene-propylene-diene copolymers and natural rubbers. In light
of the resilience performance, polybutadienes are preferred. When
other rubber is used in combination with polybutadiene, it is
preferred that polybutadiene is included as a principal component.
Specifically, the proportion of polybutadiene occupying in total
base rubber is preferably equal to or greater than 50% by weight,
and particularly preferably equal to or greater than 80% by weight.
Polybutadienes, which have a percentage of cis-1,4 bond of equal to
or greater than 40%, and particularly equal to or greater than 80%,
are preferred.
[0022] For crosslinking of the core 4, a co-crosslinking agent is
usually used. Preferable co-crosslinking agent in light of the
resilience performance is a monovalent or bivalent metal salt of an
.alpha.,.beta.-unsaturated carboxylic acid having 2 to 8 carbon
atoms. Specific examples of preferable co-crosslinking agent
include zinc acrylate, magnesium acrylate, zinc methacrylate and
magnesium methacrylate. Zinc acrylate and zinc methacrylate are
particularly preferred on the ground that a high resilience
performance can be achieved.
[0023] As a co-crosslinking agent, an .alpha.,.beta.-unsaturated
carboxylic acid having 2 to 8 carbon atoms, and an oxidized metal
may be blended. Both components react in the rubber composition to
give a salt. This salt is responsible for the crosslinking
reaction. Examples of preferable .alpha.,.beta.-unsaturated
carboxylic acid include acrylic acid and methacrylic acid. Examples
of preferable oxidized metal include zinc oxide and magnesium
oxide.
[0024] The amount of the co-crosslinking agent to be blended is
preferably 10 parts by weight or greater and 50 parts by weight or
less per 100 parts by weight of the base rubber. When the amount is
less than the above range, the resilience performance of the golf
ball 2 may become insufficient. In this respect, the amount is more
preferably equal to or greater than 15 parts by weight. When the
amount is beyond the above range, hard feel at impact of the golf
ball 2 may be experienced. In this respect, the amount is more
preferably equal to or less than 45 parts by weight.
[0025] It is preferred that an organic peroxide is blended together
with the co-crosslinking agent into the rubber composition for use
in the core 4. The organic peroxide serves as a crosslinking
initiator. By blending the organic peroxide, the resilience
performance of the golf ball 2 may be improved. Examples of
suitable organic peroxide include dicumyl peroxide,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane and di-t-butyl peroxide.
Particularly versatile organic peroxide is dicumyl peroxide.
[0026] The amount of the organic peroxide to be blended is
preferably 0.1 part by weight or greater and 3.0 parts by weight or
less per 100 parts by weight of the base rubber. When the amount is
less than the above range, the resilience performance of the golf
ball 2 may become insufficient. In this respect, the amount is more
preferably equal to or greater than 0.3 part by weigh, and
particularly preferably equal to or greater than 0.5 part by
weight. When the amount is beyond the above range, hard feel at
impact of the golf ball 2 may be experienced. In this respect, the
amount is more preferably equal to or less than 2.5 parts by
weight.
[0027] A filler may be blended into the core 4 for the purpose of
adjusting specific gravity and the like. Illustrative examples of
suitable filler include zinc oxide, barium sulfate, calcium
carbonate and magnesium carbonate. Also, powder of a highly dense
metal may be blended as a filler. Specific examples of the highly
dense metal include tungsten and molybdenum. The amount of the
filler to be blended is determined ad libitum so that the intended
specific gravity of the core 4 can be accomplished. Particularly
preferable filler is zinc oxide. Zinc oxide serves not only in
adjusting specific gravity but also as a crosslinking activator.
Various kinds of additives such as sulfur, a sulfur compound, an
anti-aging agent, a coloring agent, a plasticizer, a dispersant and
the like may be blended in an appropriate amount to the core 4 as
needed. The core 4 may be also blended with crosslinked rubber
powder or synthetic resin powder.
[0028] Amount of compressive deformation of the core 4 is
preferably equal to or less than 5.0 mm, more preferably equal to
or less than 4.5 mm, and particularly preferably equal to or less
than 4.0 mm. When the golf ball 2 is hit with a driver, the core 4
is deformed greatly in conjunction with the cover 10 and the mid
layer 6. The core 4 having a small amount of compressive
deformation is responsible for a flight performance upon a shot
with a driver. Too small amount of compressive deformation may
result in deteriorated feel at impact. In light of the feel at
impact, the amount of compressive deformation is preferably equal
to or greater than 1.5 mm, and particularly preferably equal to or
greater than 2.0 mm.
[0029] For the measurement of the amount of compressive
deformation, a core 4 is first placed on a hard plate made of
metal. Next, a cylinder made of metal gradually descends toward the
core 4. Accordingly, the core 4, which is sandwiched between the
bottom face of the cylinder and the hard plate, is deformed. A
migration distance of the cylinder, starting from the state in
which initial load of 98 N is applied to the core 4 up to the state
in which final load of 1274 N is applied thereto is the amount of
compressive deformation.
[0030] The core 4 preferably has a diameter of 25 mm or greater and
41.5 mm or less. The core 4 preferably has a weight of 25 g or
greater and 42 g or less. Crosslinking temperature of the core 4 is
usually 140.degree. C. or greater and 180.degree. C. or less. The
crosslinking time period of the core 4 is usually 10 minutes or
longer and 60 minutes or less. The core 4 may be formed with two or
more layers.
[0031] A thermoplastic resin composition is suitably used for the
mid layer 6. Examples of the base polymer of the resin composition
include ionomer resins, thermoplastic polyester elastomers,
thermoplastic polyamide elastomers, thermoplastic polyurethane
elastomers, thermoplastic polyolefin elastomers and thermoplastic
polystyrene elastomers. In particular, ionomer resins are
preferred. Ionomer resins are highly elastic. The ionomer resin is
responsible for a flight performance upon a shot with a driver.
[0032] Other resin may be used in combination with the ionomer
resin. In case of the use in combination, the ionomer resin is
included as a principal component of the base polymer in light of
the flight performance. Proportion of the ionomer resin occupying
in the total base polymer is preferably equal to or greater than
50% by weight, more preferably equal to or greater than 70% by
weight, and particularly preferably equal to or greater than 85% by
weight.
[0033] Preferably, an ionomer resin is used that is a copolymer of
.alpha.-olefin and an .alpha.,.beta.-unsaturated carboxylic acid
having 3 to 8 carbon atoms in which a part of the carboxylic acid
is neutralized with a metal ion. Examples of preferable
.alpha.-olefin include ethylene and propylene. Examples of
preferable .alpha.,.beta.-unsaturated carboxylic acid include
acrylic acid and methacrylic acid. Illustrative examples of the
metal ions for use in the neutralization include sodium ion,
potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion,
aluminum ion and neodymium ion. The neutralization may also be
carried out with two or more kinds of the metal ions. In light of
the resilience performance and durability of the golf ball 2,
particularly suitable metal ions are sodium ion, zinc ion, lithium
ion and magnesium ion.
[0034] Specific examples of the ionomer resin include trade names
"Himilan 1555", "Himilan 1557", "Himilan 1605", "Himilan 1706",
"Himilan 1707", "Himilan AM7311", "Himilan AM7315", "Himilan
AM7317", "Himilan AM7318" and "Himilan MK7320", available from Du
Pont-MITSUI POLYCHEMICALS Co., Ltd.; trade names "Surlyn.RTM.
7930", "Surlyn.RTM. 7940", "Surlyn.RTM. 8140", "Surlyn.RTM. 8940",
"Surlyn.RTM. 8945", "Surlyn.RTM. 9120", "Surlyn.RTM. 9910" and
"Surlyn.RTM. 9945", available from Dupont; and trade names "IOTEK
7010", "IOTEK 7030", "IOTEK 8000" and "IOTEK 8030", available from
EXXON Corporation. Two or more kinds of ionomer resins may be used
in combination.
[0035] Into the resin composition of the mid layer 6 may be blended
a filler for the purpose of adjusting specific gravity and the
like. Illustrative examples of suitable filler include zinc oxide,
barium sulfate, calcium carbonate and magnesium carbonate. Powder
of a highly dense metal may be also blended as a filler. Specific
examples of the highly dense metal include tungsten and molybdenum.
The amount of the filler to be blended is determined ad libitum so
that the intended specific gravity of the mid layer 6 can be
accomplished. Into the mid layer 6 may be also blended a coloring
agent, crosslinked rubber powder or synthetic resin powder.
[0036] In light of the flight performance upon a shot with a
driver, hardness Hm of the mid layer 6 is preferably equal to or
greater than 55, more preferably equal to or greater than 58, and
particularly preferably equal to or greater than 60. When the
hardness Hm is extremely great, to achieve a favorable feeling upon
impact of the golf ball 2 may become difficult. In this respect,
the hardness Hm is preferably equal to or less than 72, more
preferably equal to or less than 70, and particularly preferably
equal to or less than 68.
[0037] In the present invention, the hardness Hm of the mid layer 6
and the hardness Hc of the cover 10 are measured in accordance with
a standard of "ASTM-D 2240-68". For the measurement, an automated
rubber hardness scale which is equipped with a Shore D type spring
hardness scale (trade name "LA1", available from Koubunshi Keiki
Co., Ltd.) is used. For the measurement, a sheet which is formed by
hot press is used having a thickness of about 2 mm and consisting
of the same material as the mid layer 6 (or the cover 10). Prior to
the measurement, the sheet is stored at a temperature of 23.degree.
C. for two weeks. When the measurement is carried out, three sheets
are overlaid.
[0038] Thickness Tm of the mid layer 6 is preferably 0.3 mm or
greater and 2.5 mm or less. When the thickness Tm is less than the
above range, a flight performance upon a shot with a driver may
become insufficient. In this respect, the thickness Tm is more
preferably equal to or greater than 0.5 mm, and particularly
preferably equal to or greater than 0.7 mm. When the thickness Tm
is beyond the above range, to achieve a favorable feeling upon
impact of the golf ball 2 may become difficult. In this respect,
the thickness Tm is more preferably equal to or less than 2.0
mm.
[0039] In light of adhesion between the mid layer 6 and the
reinforcing layer 8 or the cover 10, the surface of the mid layer 6
is preferably subjected to a surface treatment to increase the
roughness thereof. Specific examples of the treatment include
brushing, grinding and the like.
[0040] The reinforcing layer 8 lies between the mid layer 6 and the
cover 10 to elevate the adhesiveness therebetween. As described
later, the cover 10 of this golf ball 2 is very thin. When such a
thin cover 10 is hit with an edge of a clubface, a wrinkle is
liable to be generated. The reinforcing layer 8 suppresses
generation of such a wrinkle.
[0041] For the base polymer of the reinforcing layer 8, a
two-component cured thermosetting resin may be suitably used.
Specific examples of the two-component cured thermosetting resin
include epoxy resins, urethane resins, acrylic resins, polyester
based resins and cellulose based resins. In light of the mechanical
strength (e.g., strength at break) and durability of the
reinforcing layer 8, two-component cured epoxy resins and
two-component cured urethane resins are preferred.
[0042] The two-component cured epoxy resin is obtained by curing an
epoxy resin with a polyamide based curing agent. Illustrative
examples of the epoxy resin for use in the two-component cured
epoxy resin include bisphenol A type epoxy resin, bisphenol F type
epoxy resin and bisphenol AD type epoxy resin. The bisphenol A type
epoxy resin is obtained by a reaction of bisphenol A with an epoxy
group-containing compound such as epichlorohydrin. The bisphenol F
type epoxy resin is obtained by a reaction of bisphenol F with an
epoxy group-containing compound. The bisphenol AD type epoxy resin
is obtained by a reaction of bisphenol AD with an epoxy
group-containing compound. In light of the balance among softness,
chemical resistance, heat resistance and toughness, bisphenol A
type epoxy resins are preferred.
[0043] The polyamide based curing agent has multiple amino groups
and one or more amide groups. This amino group can react with an
epoxy group. Specific examples of the polyamide based curing agent
include polyamide amine curing agents and denatured products of the
same. The polyamide amine curing agent is obtained by a
condensation reaction of a polymerized fatty acid with a polyamine.
Typical polymerized fatty acid may be obtained by heating natural
occurring fatty acids containing large amounts of unsaturated fatty
acids such as linoleic acid, linolenic acid and the like in the
presence of a catalyst to perfect the synthesis. Specific examples
of the unsaturated fatty acid include tall oil, soybean oil,
linseed oil and fish oil. A polymerized fatty acids having a dimer
content of equal to or greater than 90% by weight and a trimer
content of equal to or less than 10% by weight, and being
hydrogenated are preferred. Illustrative examples of preferred
polyamine include polyethylene diamine, polyoxyalkylene diamine and
derivatives thereof.
[0044] Upon mixing of the epoxy resin and the polyamide based
curing agent, ratio of epoxy equivalent of the epoxy resin and
amine active hydrogen equivalent of the polyamide based curing
agent is preferably 1.0/1.4 or greater and 1.0/1.0 or less.
[0045] The two-component cured urethane resin is obtained by a
reaction of a base material and a curing agent. A two-component
cured urethane resin obtained by a reaction of a base material
containing a polyol component with a curing agent containing
polyisocyanate or a derivative thereof, or a two-component cured
urethane resin obtained by a reaction of a base material containing
isocyanate group-ended urethane prepolymer with a curing agent
having an active hydrogen may be used. In particular, two-component
cured urethane resins prepared by a reaction of a base material
containing a polyol component with a curing agent containing
polyisocyanate or a derivative thereof are preferred.
[0046] It is preferred that urethane polyol is used as the polyol
component of the base material. The urethane polyol has urethane
bonds and at least two hydroxyl groups. Preferably, the urethane
polyol has a hydroxyl group at its end. The urethane polyol may be
obtained by allowing polyol and polyisocyanate to react at a ratio
such that an excessive molar ratio of the hydroxyl group of the
polyol component to the isocyanate group of polyisocyanate is
attained.
[0047] The polyol for use in production of the urethane polyol has
multiple hydroxyl groups. Polyol having a weight average molecular
weight of 50 or greater and 2000 or less, and particularly 100 or
greater and 1000 or less is preferred. Examples of the polyol
having a low molecular weight include diol and triol. Specific
examples of the diol include ethylene glycol, diethylene glycol,
triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl
glycol and 1,6-hexanediol. Specific examples of the triol include
trimethylolpropane and hexanetriol. Examples of the polyol having a
high molecular weight include polyether polyols such as
polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG) and
polyoxytetramethylene glycol (PTMG); condensed polyester polyols
such as polyethylene adipate (PEA), polybutylene adipate (PBA) and
polyhexamethylene adipate (PHMA); lactone based polyester polyols
such as poly-.epsilon.-caprolactone (PCL); polycarbonate polyols
such as polyhexamethylene carbonate; and acrylic polyols. Two or
more kinds of polyols may be used in combination.
[0048] Polyisocyanate for use in production of urethane polyol has
multiple isocyanate groups. Specific examples of the polyisocyanate
include aromatic polyisocyanates such as 2,4-toluene diisocyanate,
2,6-toluene diisocyanate, mixtures of 2,4-toluene diisocyanate and
2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate
(MDI) 1,5-naphthylene diisocyanate (NDI),
3,3'-bitolylene-4,4'-diisocyanate (TODI), xylylene diisocyanate
(XDI), tetramethylxylylene diisocyanate (TMXDI) and paraphenylene
diisocyanate (PPDI), alicyclic polyisocyanates such as
4,4'-dicyclohexylmethane diisocyanate (H.sub.12MDI), hydrogenated
xylylene diisocyanate (H.sub.6XDI), hexamethylene diisocyanate
(HDI) and isophorone diisocyanate (IPDI); and aliphatic
polyisocyanates. Two or more polyisocyanates may be used in
combination. In light of the weather resistance, TMXDI, XDI, HDI,
H.sub.6XDI, IPDI and H.sub.12MDI are preferred.
[0049] In the reaction of polyol and polyisocyanate for producing
the urethane polyol, any known catalyst may be used. Typical
catalyst may be dibutyltin dilaurate.
[0050] In light of strength of the reinforcing layer 8, ratio of
the urethane bonds included in the urethane polyol is preferably
equal to or greater than 0.1 mmol/g. In light of the following
capability of the reinforcing layer 8 to the cover 10, the ratio of
the urethane bonds included in the urethane polyol is preferably
equal to or less than 5 mmol/g. The ratio of the urethane bonds may
be adjusted by adjusting the molecular weight of the polyol to be a
raw material, and by adjusting compounding ratio of the polyol and
the polyisocyanate.
[0051] In light of a short time period required for the reaction of
the base material with the curing agent, the urethane polyol has a
weight average molecular weight of preferably equal to or greater
than 4000, and more preferably equal to or greater than 4500. In
light of the adhesiveness of the reinforcing layer 8, the urethane
polyol has a weight average molecular weight of preferably equal to
or less than 10000, and more preferably equal to or less than
9000.
[0052] In light of the adhesiveness of the reinforcing layer 8, the
urethane polyol has a hydroxyl value (mgKOH/g) of preferably equal
to or greater than 15, and more preferably equal to or greater than
73. In light of a short time period required for the reaction of
the base material with the curing agent, the urethane polyol has a
hydroxyl value of preferably equal to or less than 130, and more
preferably equal to or less than 120.
[0053] The base material may contain, in addition to the urethane
polyol, a polyol not having any urethane bond. The aforementioned
polyol that is a raw material of the urethane polyol may be used in
the base material. Polyols that are miscible with the urethane
polyol are preferred. In light of a short time period required for
the reaction of the base material with the curing agent, proportion
of the urethane polyol in the base material is preferably equal to
or greater than 50% by weight and more preferably equal to or
greater than 80% by weight based on the solid content. Ideally,
this proportion is 100% by weight.
[0054] The curing agent contains polyisocyanate or a derivative
thereof. The aforementioned polyisocyanate that is a raw material
of the urethane polyol may be used in the curing agent.
[0055] The reinforcing layer 8 may include additives such as a
coloring agent (typically, titanium dioxide), a phosphate based
stabilizer, an antioxidant, a light stabilizer, a fluorescent
brightening agent, an ultraviolet absorbent, a blocking preventive
agent and the like. The additive may be added to the base material
of the two-component cured thermosetting resin, or may be added to
the curing agent.
[0056] The reinforcing layer 8 is obtained by coating a liquid,
which is prepared by dissolving or dispersing a base material and a
curing agent in a solvent, on the surface of the mid layer 6. In
light of the workability, coating with a spray gun is preferred.
The solvent is volatilized after the coating to permit a reaction
of the base material with the curing agent thereby forming the
reinforcing layer 8. Illustrative examples of preferred solvent
include toluene, isopropyl alcohol, xylene, methyl ethyl ketone,
methyl isobutyl ketone, ethylene glycol monomethyl ether,
ethylbenzene, propylene glycol monomethyl ether, isobutyl alcohol
and ethyl acetate.
[0057] In light of suppression of a wrinkle, the reinforcing layer
8 has a thickness of preferably equal to or greater than 3 .mu.m,
and more preferably equal to or greater than 5 .mu.m. In light of
easy formation of the reinforcing layer 8, it is preferred that the
thickness is equal to or less than 300 .mu.m, still more, equal to
or less than 100 .mu.m, yet more, equal to or less than 50 .mu.m,
and further, equal to or less than 20 .mu.m. The thickness is
measured by observation of the cross section of the golf ball 2
with a micro scope. When the surface of the mid layer 6 has
roughness resulting from the surface roughening treatment, the
thickness is measured immediately above the protruded portion.
[0058] In light of suppression of the wrinkle, the reinforcing
layer 8 has a pencil hardness of preferably equal to or greater
than 4B, and more preferably equal to or greater than B. In light
of small loss of the force during transfer from the cover 10 to the
mid layer 6 upon hit of the golf ball 2, the reinforcing layer 8
has a pencil hardness of preferably equal to or less than 3H. The
pencil hardness is measured in accordance with a standard of "JIS
K5400".
[0059] When sufficient adhesion between the mid layer 6 and the
cover 10 is accomplished leading to less possibility to generate a
wrinkle, the reinforcing layer 8 may not be provided.
[0060] A thermoplastic resin composition is suitably used for the
cover 10. Examples of base polymer of this resin composition
include thermoplastic polyurethane elastomers, thermoplastic
polyester elastomers, thermoplastic polyamide elastomers,
thermoplastic polyolefin elastomers, thermoplastic polystyrene
elastomers and ionomer resins. In particular, thermoplastic
polyurethane elastomers are preferred. The thermoplastic
polyurethane elastomers are soft. Great spin rate is achieved upon
hit with a short iron of the golf ball 2 having a cover 10
comprising a thermoplastic polyurethane elastomer. The cover 10
comprising a thermoplastic polyurethane elastomer is responsible
for a control performance upon a shot with a short iron. The
thermoplastic polyurethane elastomer is also responsible for the
scuff resistance of the cover 10.
[0061] Other resin may be used in combination with the
thermoplastic polyurethane elastomer. In light of the control
performance, the thermoplastic polyurethane elastomer is included
in the base polymer as a principal component when used in
combination. Proportion of the thermoplastic polyurethane elastomer
occupying in total base polymer is preferably equal to or greater
than 50% by weight, more preferably equal to or greater than 70% by
weight, and particularly preferably equal to or greater than 85% by
weight.
[0062] The thermoplastic polyurethane elastomer includes a
polyurethane component as a hard segment, and a polyester component
or a polyether component as a soft segment. Illustrative examples
of the curing agent for the polyurethane component include
alicyclic diisocyanate, aromatic diisocyanate and aliphatic
diisocyanate. In particular, alicyclic diisocyanate is preferred.
Because the alicyclic diisocyanate has no double bond in the main
chain, yellowing of the cover 10 can be suppressed. Additionally,
because the alicyclic diisocyanate is excellent in strength, the
cover 10 can be prevented from being scuffed. Two or more kinds of
diisocyanates may be used in combination.
[0063] Illustrative examples of the alicyclic diisocyanate include
4,4'-dicyclohexylmethane diisocyanate (H.sub.12MDI),
1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6XDI), isophorone
diisocyanate (IPDI) and trans-1,4-cyclohexane diisocyanate (CHDI).
In light of versatility and processability, H.sub.12MDI is
preferred.
[0064] Illustrative examples of the aromatic diisocyanate include
4,4'-diphenylmethane diisocyanate (MDI) and toluene diisocyanate
(TDI). Illustrative examples of the aliphatic diisocyanate include
hexamethylene diisocyanate (HDI).
[0065] Specific examples of the thermoplastic polyurethane
elastomer include trade name "Elastolan XNY90A", trade name
"Elastolan XNY97A", trade name "Elastolan XNY585" and trade name
"Elastolan XKP016N", available from BASF Japan Ltd; and trade name
"Rezamin P4585LS" and trade name "Rezamin PS62490", available from
Dainichiseika Color & Chemicals Mfg. Co., Ltd.
[0066] Into the cover 10 may be blended a coloring agent such as
titanium dioxide, a filler such as barium sulfate, a dispersant, an
antioxidant, an ultraviolet absorbent, a light stabilizer, a
fluorescent agent, a fluorescent brightening agent and the like in
an appropriate amount as needed. Also, the cover 10 may be blended
with powder of a highly dense metal such as tungsten, molybdenum or
the like for the purpose of adjusting the specific gravity.
[0067] The cover 10 has a Shore D hardness Hc of equal to or less
than 54. By employing such a soft cover 10, a favorable control
performance may be achieved upon a shot with a short iron. In light
of the control performance, it is preferred that the hardness Hc is
equal to or less than 50, still more, equal to or less than 47, and
further, equal to or less than 42. When the hardness is too small,
a flight performance upon a shot with a driver, a long iron and a
middle iron may be insufficient. In this respect, it is preferred
that the hardness Hc is equal to or greater than 20, still more,
equal to or greater than 28, and further, equal to or greater than
33.
[0068] The cover 10 has a thickness Tc of equal to or less than 0.6
mm. As described above, the cover 10 has a low hardness. The cover
10 having such a low hardness is disadvantageous in terms of
resilience coefficient of the golf ball 2. Upon a shot with a
driver, the mid layer 6 as well as the core 4 of the golf ball 2 is
deformed greatly. By setting the thickness Tc to be equal to or
less than 0.6 mm, the cover 10 does not adversely affect the
resilience coefficient to a large extent upon a shot with a driver,
even though the cover 10 has a low hardness. An excellent flight
performance can be achieved upon a shot with a driver through using
the ionomer resin in the mid layer 6.
[0069] In light of the flight performance, the thickness Tc is more
preferably equal to or less than 0.5 mm, and particularly
preferably equal to or less than 0.4 mm. When the thickness Tc is
too small, a difficulty may be involved in forming the cover 10. In
this respect, the thickness Tc is preferably equal to or greater
than 0.1 mm, and more preferably equal to or greater than 0.2
mm.
[0070] The cover 10 has a volume V of equal to or less than 3.0
cm.sup.3. Spin rate yielded upon hit of the golf ball 2 with a long
iron or a middle iron predominantly depends on deformative behavior
of the cover 10. Amount of deformation of the cover 10 can be
reduced by setting the volume V of the cover 10 to be equal to or
less than 3.0 cm.sup.3, irrespective of small hardness Hc. The spin
rate yielded upon hit of the golf ball 2 with a long iron or a
middle iron is low. Low spin rate leads to a great flight distance.
This golf ball 2 is excellent in a flight performance upon a shot
with a long iron and a middle iron.
[0071] In light of the flight performance, the volume V is
preferably equal to or less than 2.7 cm.sup.3, more preferably
equal to or less than 2.4 cm.sup.3, and particularly preferably
equal to or less than 2.2 cm.sup.3. When the volume V is too small,
a difficulty may be involved in forming the cover 10. In this
respect, the volume V is preferably equal to or greater than 0.3
cm.sup.3, and more preferably equal to or greater than 1.0
cm.sup.3.
[0072] In this golf ball 2, a product (Tc * Hc * V) obtained by
multiplying the thickness Tc (mm), the hardness Hc and the volume V
(cm.sup.3) is equal to or less than 90. This golf ball 2 easily
gets on a clubface upon impact with a driver, and can be favorably
delivered from the club. Such getting on a clubface is responsible
for stabilization of the launch direction of the golf ball 2.
Favorable delivery results in a light feel at impact. According to
this golf ball 2, an excellent feeling is experienced.
[0073] In light of the feeling, the product (Tc * Hc * V) is
preferably equal to or less than 85, more preferably equal to or
less than 82, and particularly preferably equal to or less than 60.
The product (Tc * Hc * V) is usually equal to or greater than
1.0.
[0074] In light of the feeling, a product (Hc * V) obtained by
multiplying the hardness Hc and the volume V (cm.sup.3) is
preferably equal to or less than 140, and more preferably equal to
or less than 115. The product (Hc * V) is usually equal to or
greater than 10.
EXAMPLES
Example 1
[0075] A rubber composition was obtained by kneading 100 parts by
weight of polybutadiene (trade name "BR-730", available from JSR
Corporation), 35 parts by weight of zinc diacrylate, an appropriate
amount of zinc oxide, 0.7 part by weight of
bis(pentabromophenyl)disulfide and 0.9 part by weight of dicumyl
peroxide. This rubber composition was placed into a mold having
upper and lower mold half each having a hemispherical cavity, and
heated under a temperature of 170.degree. C. for 15 minutes to
obtain a core having a diameter of 38.5 mm. This core had a weight
of 34.9 g.
[0076] A resin composition was obtained by kneading 50 parts by
weight of an ionomer resin (Himilan 1605, described above) 50 parts
by weight of other ionomer resin (Surlyn.RTM. 9945, described
above), 4 parts by weight of titanium dioxide and 0.1 part by
weight of a coloring agent (ultramarine blue) in a biaxial
extruder. This resin composition was rendered to cover around the
core by injection molding to obtain a mid layer. This mid layer had
a hardness Hm of 63.
[0077] A coating composition containing a two-component cured epoxy
resin as a base polymer (trade name "Polin 750LE", available from
Shinto Paint Co., Ltd.) was prepared. The base material liquid of
this coating composition consists of 30 parts by weight of
bisphenol A type solid epoxy resin and 70 parts by weight of a
solvent. The curing agent liquid of this coating composition
consists of 40 parts by weight of denatured polyamide amine, 55
parts by weight of a solvent and 5 parts by weight of titanium
dioxide. Weight ratio of the base material liquid and the curing
agent liquid is 1/1. This coating composition was coated on the
surface of the mid layer with a spray gun, and kept in an
atmosphere of 40.degree. C. for 24 hours to give a reinforcing
layer.
[0078] A type d resin composition shown in Table 1 below was
obtained with a biaxial extruder. Half shells were obtained from
this resin composition with compression molding. A spherical body
comprising the core, the mid layer and the reinforcing layer were
covered by two pieces of the half shell, which was placed into a
mold having upper and lower mold half each having a hemispherical
cavity to obtain a cover with compression molding. A paint layer
was formed around this cover to give a golf ball of Example 1. This
golf ball had a diameter of 42.7 mm. TABLE-US-00001 TABLE 1
Specification of cover Type a b c d e f Rezamin PS62490 100 -- --
-- -- -- Rezamin P4585LS -- 100 -- -- -- -- Elastolan XNY90A -- --
100 -- -- -- Elastolan XNY97A -- -- -- 100 35 -- Elastolan XKP016N
-- -- -- -- 65 100 Titanium dioxide 4 4 4 4 4 4 Ultramarine blue
0.1 0.1 0.1 0.1 0.1 0.1 Hardness (Shore D) 28 33 42 47 54 58
Examples 2 to 10 and Comparative Examples 1 to 3
[0079] In a similar manner to Example 1, golf balls with
specifications as presented in Table 2 and Tale 3 below were
obtained. A coating composition comprising a two-component cured
urethane resin as a base polymer was used in the reinforcing layer
in Example 4. In production of this coating composition, 116 parts
by weight of PTMG and 16 parts by weight of 1,2,6-hexanetriol were
first dissolved in 120 parts by weight of a solvent (mixed liquid
of toluene and methyl ethyl ketone). To this solution was added
dibutyltin dilaurate to give the concentration of 0.1% by weight.
To this solution was added 48 parts by weight of isophorone
diisocyanate dropwise while keeping at 80.degree. C. to obtain a
base material liquid containing urethane polyol. Solid content of
this urethane polyol was 60% by weight, with a hydroxyl value being
87 mgKOH/g, and with a weight average molecular weight being 7850.
This base material liquid and a curing agent liquid containing
isophorone diisocyanate (manufactured by Sumitomo Bayer Urethane
Co., Ltd.) were mixed to give a molar ratio of NCO/OH being 1.2. To
this liquid were added a light stabilizer (trade name "Sanol
LS770", available from Sankyo Co., Ltd.), an ultraviolet ray
absorbing agent (trade name "TINUVIN.RTM. 900", available from
Ciba-Geigy Co.) and a fluorescent brightening agent (trade name
"UVITEX.RTM. OB", available from Ciba-Geigy Co.") to prepare a
coating composition. Amounts as added per 100 parts by weight of
the urethane resin component are 2 parts by weight for the light
stabilizer, 2 parts by weight for the ultraviolet ray absorbing
agent and 0.2 part by weight of the fluorescent brightening
agent.
[0080] [Shot with Driver]
[0081] A driver with a metal head was attached to a swing machine
available from Golf Laboratory Co. Then the machine condition was
set to give the head speed of 50 m/sec, and the golf balls were hit
therewith. Accordingly, ball speed immediately after the hit and
travel distance (i.e., the distance from the launching point to the
point where the ball stopped) were measured. Mean values of 10
times measurement are shown in Table 2 and Table 3 below.
[0082] [Shot with Middle Iron]
[0083] To the swing machine described above was attached a number
five iron. Then the machine condition was set to give the head
speed of 41 m/sec, and the golf balls were hit therewith.
Accordingly, spin rate immediately after the hit and travel
distance were measured. Mean values of 10 times measurement are
shown in Table 2 and Table 3 below.
[0084] [Shot with Short Iron]
[0085] To the swing machine described above was attached an
approach wedge. Then the machine condition was set to give the head
speed of 21 m/sec, and the golf balls were hit therewith.
Accordingly, spin rate immediately after the hit was measured. Mean
values of 10 times measurement are shown in Table 2 and Table 3
below.
[0086] [Evaluation of Feeling]
[0087] Using a driver, the golf balls were hit by a high-level golf
player. Then, the golf player rated the feeling into four ranks of
from A to D based on the following criteria: [0088] A: extremely
satisfactory; [0089] B: satisfactory; [0090] C: somewhat
unsatisfactory; and [0091] D: unsatisfactory. The results are
presented in Table 2 and Table 3 below.
[0092] [Evaluation of Extent of Wrinkle Generation]
[0093] To the swing machine described above was attached a pitching
wedge. Machine height was adjusted such that the golf ball is hit
at a leading edge of the club head. Then the machine condition was
set to give the head speed of 37 m/sec, and the golf balls were hit
therewith. Accordingly, the surface of the golf ball was visually
observed, and the extent of a wrinkle was rated into four ranks of
from A to D based on the following criteria: [0094] A: wrinkle
hardly generated; [0095] B: wrinkle slightly generated; [0096] C:
wrinkle greatly generated; and [0097] D: wrinkle greatly generated,
with exposed mid layer. The results are presented in Table 2 and
Table 3 below.
[0098] [Evaluation of Durability]
[0099] The golf balls were rendered to hit on a metal plate
repeatedly at a velocity of 45 m/s. Durability was rated into four
ranks of from A to D based on the following criteria: [0100] A: no
breakage caused on 150 times hitting; [0101] B: no breakage caused
on 100 times hitting, although breakage caused on 150 times
hitting; [0102] C: no breakage caused on 50 times hitting, although
breakage caused on 100 times hitting; and
[0103] D: breakage caused on 50 times hitting. The measurement was
carried out on 6 golf balls. The results of rating which gave a
maximum convergence are presented in Table 2 and Table 3 below.
TABLE-US-00002 TABLE 2 Results of evaluation Compara. Compara.
Compara. example Example Example Example example eExample Example 1
1 2 3 2 3 4 Mid layer Thickness Tm (mm) 1.4 1.5 1.5 1.5 1.5 1.5 1.5
Reinforcing layer Base polymer epoxy epoxy epoxy epoxy epoxy epoxy
polyurethane Thickness (.mu.m) 10 5 10 10 10 10 10 Cover Thickness
Tc (mm) 0.7 0.6 0.6 0.6 0.6 0.6 0.6 Type d d c d e f d Hardness Hc
47 47 42 47 54 58 47 Volume V (cm.sup.3) 3.63 2.91 2.91 2.91 2.91
2.91 2.91 Tc*Hc*V 119.5 82.0 73.3 82.0 94.2 101.4 82.0 Hc*V 170.6
136.7 122.2 136.7 157.1 168.8 136.7 Shot with driver Ball speed
(m/s) 72.5 72.7 72.6 72.6 72.9 73.0 72.7 Travel distance (m) 273.4
275.2 274.6 274.8 277.1 277.1 275.2 Shot with #5 iron Spin rate
(rpm) 4850 4700 4800 4700 4650 4550 4700 Travel distance (m) 171.0
173.7 172.7 173.9 173.7 175.6 173.7 Spin rate upon shot with 6700
6700 6800 6750 6200 5900 6700 approach wedge (rpm) Feeling D A A A
B C A Extent of wrinkle A A A A A A A Durability A A A A A A A
[0104] TABLE-US-00003 TABLE 3 Results of evaluation Example Example
Example Example Example Example 5 6 7 8 9 10 Mid layer Thickness Tm
(mm) 1.5 1.6 1.6 2.0 2.0 2.0 Reinforcing layer Base polymer --
epoxy epoxy epoxy epoxy epoxy Thickness (.mu.m) -- 10 10 10 10 50
Cover Thickness Tc (mm) 0.6 0.5 0.5 0.1 0.1 0.1 Type d d e a b b
Hardness Hc 47 47 54 28 33 33 Volume V (cm.sup.3) 2.91 2.36 2.36
0.55 0.55 0.55 Tc*Hc*V 82.0 55.5 63.7 1.8 1.8 1.8 Hc*V 136.7 110.9
127.4 15.4 18.2 18.2 Shot with driver Ball speed (m/s) 72.7 72.8
73.1 73.2 73.1 73.3 Travel distance (m) 275.2 276.1 277.4 279.7
278.0 278.4 Shot with #5 iron Spin rate (rpm) 4700 4650 4400 4500
4350 4300 Travel distance (m) 173.7 174.7 177.4 177.9 178.3 178.6
Spin rate upon shot with 6700 6700 6500 6850 6800 6800 approach
wedge (rpm) Feeling A A A A A A Extent of wrinkle D A A C B A
Durability D A A A A A
[0105] As is clear from Table 2 and Table 3, the golf ball of each
of Examples is excellent in the flight performance upon shots with
a driver and a middle iron, in the spin performance upon shots with
a short iron, and in the feeling. Accordingly, advantages of the
present invention are clearly indicated by these results of
evaluation.
[0106] The description herein above is merely for illustrative
examples, and various modifications can be made without departing
from the principles of the present invention.
* * * * *